<template>
  <el-select
    ref="selectblur"
    :value="valueTitle"
    :clearable="clearable"
    class="maxwidth"
    style="width:300px"
    :disabled="enabled"
    @clear="clearHandle"
  >
    <el-option :value="valueTitle" :label="valueTitle" class="options">
      <el-tree
        id="tree-option"
        ref="selectTree"
        :accordion="accordion"
        :data="options"
        :props="props"
        :node-key="props.value"
        :default-expanded-keys="defaultExpandedKey"
        :expand-on-click-node="false"
        @node-click="handleNodeClick"
      />
    </el-option>
  </el-select>
</template>

<script>
export default {
  name: 'ElTreeSelect',
  props: {
    // 配置项
    props: {
      type: Object,
      default: () => ({
        value: 'id', // ID字段名
        label: 'title', // 显示名称
        children: 'children' // 子级字段名
      })
    },

    // 选项列表数据(树形结构的对象数组)
    options: { type: Array, default: () => [] },

    // 初始值
    value: { type: Number, default: null },

    // 可清空选项
    clearable: { type: Boolean, default: true },

    // 自动收起
    accordion: { type: Boolean, default: false },

    enabled: { type: Boolean, default: false }
  },
  data() {
    return {
      valueId: null,
      valueTitle: '',
      defaultExpandedKey: []
    }
  },

  watch: {
    value() {
      this.valueId = ''
      this.valueTitle = ''
      this.valueId = this.value
      this.initHandle()
    }
  },
  mounted() {
    this.valueId = this.value // 初始值
    this.initHandle()
  },
  methods: {
    // 初始化值
    initHandle() {
      this.$nextTick(() => {
        if (this.$refs.selectTree.getNode(this.valueId)) {
          this.valueTitle = this.$refs.selectTree.getNode(this.valueId).data[this.props.label] // 初始化显示
        }
        this.$refs.selectTree.setCurrentKey(this.valueId)// 设置默认选中
        this.defaultExpandedKey = [this.valueId] // 设置默认展开
      })
      this.initScroll()
    },

    // 初始化滚动条
    initScroll() {
      this.$nextTick(() => {
        const scrollWrap = document.querySelectorAll(
          '.el-scrollbar .el-select-dropdown__wrap'
        )[0]
        const scrollBar = document.querySelectorAll(
          '.el-scrollbar .el-scrollbar__bar'
        )
        scrollWrap.style.cssText =
          'margin: 0px; max-height: none; overflow: hidden;'
        scrollBar.forEach(ele => (ele.style.width = 0))
      })
    },

    // 切换选项
    handleNodeClick(node) {
      this.$refs.selectblur.blur()// 让下拉框失去焦点事件
      this.valueTitle = node[this.props.label]
      this.valueId = node[this.props.value]
      this.$emit('getValue', this.valueId)
      this.defaultExpandedKey = []
    },

    // 清除选中
    clearHandle() {
      this.valueTitle = ''
      this.valueId = null
      this.defaultExpandedKey = []
      this.clearSelected()
      this.$emit('getValue', null)
    },

    // 清空选中样式
    clearSelected() {
      const allNode = document.querySelectorAll('#tree-option .el-tree-node')
      allNode.forEach(element => element.classList.remove('is-current'))
    }
  }
}
</script>

<style scoped>
.el-scrollbar .el-scrollbar__view .el-select-dropdown__item {
  height: auto;
  max-height: 274px;
  padding: 0;
  overflow: hidden;
  overflow-y: auto;
}
.el-select-dropdown__item.selected {
  font-weight: normal;
}
ul li >>> .el-tree .el-tree-node__content {
  height: auto;
  padding: 0 20px;
}
.el-tree-node__label {
  font-weight: normal;
}
.el-tree >>> .is-current .el-tree-node__label {
  color: #409eff;
  font-weight: 700;
}
.el-tree >>> .is-current .el-tree-node__children .el-tree-node__label {
  color: #606266;
  font-weight: normal;
}
.maxwidth {
  width: 100%;
}
</style>
